It's a 10-15 minute walk to Boardwalk from Studios. I'd add another 10 or so to get to Epcot. Then another 10-15 to walk through Epcot to the Land pavilion. The faster you walk, the sooner you'll make it. It's a lot of walking, too, considering that you also have to walk through Epcot.
The boat from DHS to Epcot takes about 30 minutes, then you still have to walk from the International Gateway to the Land. This doesn't include time spent at DHS waiting for the boat, if you have any.
The bus ride from DHS to Epcot itself would take about 10-15 minutes, then another 10 or so to walk from the bus stop, enter the park from the front gate and walk to the Land. The wild card here is waiting time. If you just miss a bus, it could take some time for another to arrive.